Differential Cytotoxicity but Augmented IFN-γ Secretion by NK Cells after Interaction with Monocytes from Humans, and Those from Wild Type and Myeloid-Specific COX-2 Knockout Mice.

Han-Ching Tseng,Kawaljit Kaur,Anahid Jewett,Anna Kozlowska,Paytsar Topchyan,Aida Arasteh

doi:10.3389/fimmu.2015.00259

Abstract

The list of genes, which augment NK cell function when knocked out in neighboring cells is increasing, and may point to the fundamental function of NK cells targeting cells with diminished capability to differentiate optimally since NK cells are able to target less differentiated cells, and aid in their differentiation. In this paper, we aimed at understanding the effect of monocytes from targeted knockout of COX-2 in myeloid cells (Cox-2flox/flox;LysMCre/+) and from control littermates (Cox-2flox/flox;LysM+/+) on ex vivo function of NK cells. Furthermore, we compared the effect of monocytes treated with and without lipopolysaccharide (LPS) on NK cells from mice and humans. NK cells purified from Cox-2flox/flox;LysMCre/+ mice had heightened cytotoxic activity when compared to those obtained from control littermates. In addition, NK cells cultured with autologous Cox-2flox/flox;LysMCre/+ monocytes and DCs, mouse embryonic fibroblasts from global knockout COX-2, but not with knockout of COX-2 in T cells, had increased cytotoxic function as well as augmented IFN-γ secretion when compared to NK cells from control littermates cultured with monocytes. LPS inhibited NK cell cytotoxicity while increasing IFN-γ secretion when cultured in the presence of monocytes from either Cox-2flox/flox;LysMCre/+ or control littermates. In contrast to mice, NK cells from humans when cultured with monocytes lost cytotoxic function and gained ability to secrete large amounts of IFN-γ, a process, which we had previously coined as “split anergy.” Similar to mice, LPS potentiated the loss of human NK cell cytotoxicity while increasing IFN-γ secretion in the presence of monocytes. Greater loss of cytotoxicity and larger secretion of IFN-γ in NK cells induced by gene knockout cells may be important for the greater need of these cells for differentiation.

Highlights

Knockout mouse models have provided a powerful tool for the identification and elucidation of mechanisms underlying different physiological and pathological processes in mice
Natural Killer (NK) Cells Derived from Cox-2flox/flox;LysMCre/+ Mice Mediated Higher Cytotoxicity Purified NK cells obtained from spleens of control wild type (WT) littermates (Cox-2flox/flox;LysM+/+) and those with targeted knockout
The lytic units 30/106 cells were determined using inverse number of NK cells required to lyse 30% of the target cells × 100. *P < 0.05 was obtained for the difference between control WT Cox-2flox/flox;LysMCre/+ NK cell cytotoxicity against YAC-1 cells, Mouse Embryonic Fibroblasts (MEFs), or ST63

Summary

Introduction

Knockout mouse models have provided a powerful tool for the identification and elucidation of mechanisms underlying different physiological and pathological processes in mice. A closer look at several of gene knockout mouse models (Table 1) revealed the pro-inflammatory nature of the immune responses in these animals. Increased inflammatory responses can be detected in mice with knockouts of genes that affect the core function of cells, which mediate inflammation [1]. We have previously reported knockout of key genes in healthy, as well as transformed human oral tumors increased the functional activation of Natural Killer (NK) cells [2,3,4]. The prostanoids, which include prostaglandins, prostacyclins, and thromboxanes, modulate several important physiological and pathophysiological processes such as gastric mucosal integrity [26, 27], vasodilation [28, 29], allergic response [30, 31], platelet adhesion and aggregation [32, 33], wound healing [34,35,36], and water balance [37]. The involvement of COX2 in tumor development and progression has been demonstrated in numerous cancer types [42,43,44]

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